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Biomedical subjects

S Bergström

Publications and source records attributed to S Bergström.

At least 217 records · Page 12Linked to original sources
PubMed1988

Mesenterial-window hyperplasia in the lactating rat.

By examining the true mesentery adjacent to the small gut before and after weaning, as well as in age-matched controls, we found that the number of mesenteric windows, their total area, and their total DNA content increased significantly during lactation. Simultaneously, Feulgen-DNA absorption analysis in individual mesenteric cells showed that these had a normal DNA stemline, and a normal distribution within the G1-G2 range. The hyperplasia and growth developed and declined temporally somewhat parallel in the mesenterial windows and their adjacent small gut, suggesting that an as yet unknown common factor(s) governs the hyperplastic growth in both these tissues. The novel physiological, mesenterial-window hyperplasia in the lactating rat described in the present study may prove useful for studies of the mesenteric function and the regulation of cell proliferation.

Animals↗
PubMed1988

Hyperplasia of the mesenterial windows precedes that of the small gut in the streptozotocin-diabetic rat.

Hyperplastic growth of the mesenterial windows abutting the small gut occurs in lactating rats (Bergström and Norrby 1988) and chronically diabetic rats (Norrby et al. 1983). In the present study, early events in the mesenterial windows and the small gut in streptozotocin-diabetic rats were examined. The area of the mesenterial windows had already increased significantly on day 1 and hyperplasia in terms of increased DNA content, as well as an increase in histamine content (a mast-cell marker), was established from day 2 of diabetes. The increase in total mesenterial window content of DNA, histamine and protein was roughly linear and parallel from day 2 to day 19. The small-gut circumference increased transiently on day 1, but the small-gut mucosal volume was unaffected on days 1 and 2. The small-gut wet weight increased significantly from day 5, whereas elongation was not observed until day 19. The difference in time between the appearance of hyperplasia and the growth of the mesenterial windows and their adjoining gut and the rate with which the hyperplasia proceeds in the two tissues indicate that the regulatory mechanisms of early hyperplastic growth in these tissues are not identical. The factor(s) causing mesenterial window growth and hyperplasia is/are as yet unknown.

Animals↗
PubMed1987

Rift Valley fever: a sero-epidemiological survey among pregnant women in Mozambique.

Rift Valley fever (RVF) causes abortion in sheep and cattle. However, the teratogenic and abortogenic potential of RVF in humans is not known. Sera from a total of 1163 pregnant women in Mozambique were tested for RVF virus antibodies by ELISA and 28 (2%) were found to be positive. Mothers experiencing fetal death or miscarriage (155) had the same RVF virus antibody prevalence as those with normal deliveries. Analysis of maternity histories showed some indication of increased fetal wastage among women positive for RVF virus antibody. The ELISA used in this study was compared with a plaque reduction neutralization test and found to be equally sensitive and specific for the detection of RVF virus IgG antibodies.

Abortion, Spontaneous↗
PubMed1987

Effects of recA mutations on pilus antigenic variation and phase transitions in Neisseria gonorrhoeae.

Intragenic recombination between the single complete pilin gene (expression locus) and multiple, distinct, partial pilin gene copies (silent, storage loci) is thought to account for the generation of pilus antigenic diversity and piliation phase (on-off) changes exhibited by Neisseria gonorrhoeae. The mechanisms operating in the genomic rearrangements associated with these forms of pilus variation were investigated through the study of isogenic strains of gonococci bearing either wild-type or altered recA alleles. Examination of the rates of pilus phase variation and the genetic basis for changes in piliation status displayed by these strains show that recA mediated homologous recombination is required for these high frequency events and confirm that the nonpiliated state results from mutations in the expressed pilin gene. In a strain that is deficient in recA mediated homologous recombination, pilus phase variation occurs at a 100-1000-fold reduced rate and results predominantly from one class of spontaneous frameshift mutations within the pilin structural gene.

Alleles↗
PubMed1986

Gene conversion involving the pilin structural gene correlates with pilus+ in equilibrium with pilus- changes in Neisseria gonorrhoeae.

Gonococci (Gc) exhibit pilus+----pilus- "phase transitions" at high frequency, but only some of the pilus- Gc can revert to pilus+ phenotype. We examined reversible phase transitions between pilus+ Gc and a particular pilus- variant (P-rp+ phenotype) whose pilin mRNA carries a unique block of nucleotides encoding an "assembly missense" pilin polypeptide. The results show that Gc pilus+ in equilibrium with P-rp+ transitions can result from intragenic recombination in which there is nonreciprocal exchange of partially homologous DNA sequences from a partial pilin gene (in silent, storage form) into the expression locus' complete pilin gene. Hence Gc pilus phase variation, like pilus antigenic variation, can occur by gene conversion of the pilin structural gene expression locus.

Bacterial Adhesion↗
PubMed1986

Anaemia of pregnancy in Mozambique.

To establish the prevalence of anaemia in pregnant women in Mozambique and to determine the locally most important causes of the disease, 881 pregnant women were examined at nine sites in seven of Mozambique's 10 provinces. In Maputo, the capital city, an additional 91 anaemic gravidae were compared to 207 parturients chosen at random. The study comprised interviews, and clinical and laboratory investigations. Between 5 and 15% of the pregnant women at the different sites had haemoglobin (Hb) values below 90 g/l and 58% had levels below 110 g/l. Inspection of mucosal membranes detected almost all the anaemic women with Hb values below 80 g/l. Nulliparous women were more prone to be anaemic. Iron deficiency and malaria were the main causes of anaemia, with malnutrition also contributing. Occasional cases of folic acid deficiency were found among severely anaemic women but no cases of significant deficiency of vitamin B12 were encountered. Sickle cell disease was not found to contribute significantly to anaemia of pregnancy in Mozambique. The mean corpuscular haemoglobin concentration (MCHC) proved more sensitive, under these conditions, than serum ferritin in detecting iron deficiency in anaemic women. Packed cell volume (PCV) analysis may substitute Hb analysis when screening for pregnancy anaemia in Mozambique.

Anemia↗
PubMed1986

Piliation control mechanisms in Neisseria gonorrhoeae.

Gonococci (Gc) undergo pilus+ to pilus- "phase transitions" readily in vitro. In the present study we sequenced pilin mRNA from reverting, pilus- Gc by oligonucleotide primer extension and compared these pilin mRNA sequences with those expressed by their pilus+ predecessors and pilus+ revertants. The results suggest that genetic rearrangement within the pilin structural gene can generate defective pilin gene products, resulting in a pilus- phenotype. These pilus- Gc give rise to pilus+ revertants upon reconstitution of their modified pilin gene.

Bacterial Outer Membrane Proteins↗
PubMed1986

Abnormal haemoglobins among pregnant women from Mozambique.

In a survey of 601 pregnant women in Mozambique, 34 (5.6%) were sickle cell trait carriers. Beta thalassaemia trait did not appear to be common. There was a slight rise in Hb F values in 49 women of the type reported previously in early pregnancy.

Female↗
PubMed1985

Pilus- gonococcal variants. Evidence for multiple forms of piliation control.

Pilus+ to pilus- transitions of gonococci (Gc) that involve rearrangement of pilin gene DNA yield the P-n phenotype, which is incapable of reversion (to pilus+). Reversion to pilus+ is found for nonpiliated Gc that have undergone no apparent pilin gene rearrangement. Among the reverting, nonpiliated Gc, two distinct phenotypes (P-rp- and P-rp+) occur and are differentiated according to their synthesis (or lack) of pilin subunits; both P-rp- and P-rp+ Gc contain pilin-specific mRNA. The occurrence of these different pilus- phenotypes strongly suggests that several mechanisms can account for changes in the piliation status of Gc; one of these involves pilin gene rearrangement but the others apparently operate at posttranscriptional levels. Reverting pilus- Gc may have a pathogenic advantage in being able to reversibly alter their host cell adherence-promoting surface properties through high frequency transitions in piliation status.

Bacterial Outer Membrane Proteins↗
PubMed1985

A selective postcolumn o-phthalaldehyde-derivatization system for the determination of histamine in biological material by high-performance liquid chromatography.

Based on studies of the reaction between histamine and o-phthalaldehyde in alkaline solution, a method optimized for the determination of histamine in biological samples by means of HPLC and postcolumn o-phthalaldehyde derivatization has been developed. The method permits determination of histamine even at low-picomolar levels. By means of a valve, placed immediately after the column outlet, the eluent stream can be switched between the fluorimetric and an electrochemical detector system whereby electroactive biogenic amines may also be studied under the same chromatographic conditions.

Aldehydes↗
PubMed1985

Syphilis in pregnant women in Mozambique.

To establish the prevalence of syphilis in pregnant women in Mozambique and evaluate present diagnostic methods, 1468 pregnant women in eight of the country's 10 provinces were examined using the Venereal Disease Research Laboratory (VDRL) test. Positive serum samples were also analysed using the Treponema pallidum haemagglutination (TPHA) assay and one group was also analysed using the fluorescent treponemal antibody absorbed (FTA-ABS) test. The prevalence of VDRL seroreactivity was found to be between 4.5% and 14.6%, whereas the prevalence of treponemal disease as verified by TPHA or FTA-ABS tests was between 1.6% and 9.8%. It is concluded that syphilis is relatively common among pregnant women in Mozambique. The predictive value of a positive VDRL test, when adequately performed, was

Female↗
PubMed1984

On disturbance of homeostasis in organ-cultured tissue.

The intact membranous rat mesentery was cultured in Eagle's minimum essential medium containing no serum or only low concentrations of serum. The procedure is in some important respects superior to previous organ culture techniques. To estimate the extent of disturbance of homeostasis of the tissue in culture, the spontaneous mast-cell histamine release was quantitated after preculture preparation of the specimens and after different intervals in culture. Also, the proliferation of fibroblasts and mesothelial cells that predominate in the mesentery was assessed at 48 h by cytofluorometric quantitation of DNA in single-tissue cells. Spontaneous histamine release was time dependent during cultivation, amounting to ca. 50% at 48 h, and was affected by the medium used for moistening the tissue before cultivation. Culturing also brought about great spontaneous increase in the proliferation of fibroblasts and mesothelial cells, the rate being related to the concentration of serum. Addition of the mast-cell secretagogues 48/80 or polymyxin B at 1 h caused rapid release of 50 to 60% of the histamine and was followed by augmented proliferation in the serum-containing media. The spontaneous increase of cell proliferation in tissue culture may be causally related to mast-cell secretion. Further studies are needed to define factors influencing the spontaneous mast-cell secretion and the mast-cell-dependent mitogenesis in normal tissue cells.

Animals↗
PubMed1984

Characteristics of pregnant women in Mozambique--parity, child survival and socioeconomic status.

As a basis for improvement of maternal health care programmes in Mozambique, 1051 pregnant women were interviewed at 10 sites in 8 of the country's 10 provinces. Two-thirds of the women lived in rural areas. The average number of previous births ranged from 2.4 to 4.7 and was significantly correlated to the proportion of children lost before 5 years of age. Child survival was significantly higher when the woman had received some education, possessed a radio, or the woman or her husband had paid employment. In the most underprivileged rural area, 56% of the children had died before the age of 5 and 35% of the pregnant women had undergone 6 childbirths or more. It is concluded that in order to improve maternal and child health it is necessary to increase socioeconomic development as well as improve maternal and child health care.

Adolescent↗